This invention relates to an apparatus and method for creating a structure with complex external and internal shapes. In a preferred embodiment of the invention, the invention relates to an apparatus and method for creating dental crowns with complex external and internal shapes.
A variety of means and methods have been developed over the years for creating structures from molds. A continuing problem is the creation of structures with complex external shapes. The difficulty with preparing molds with complex shapes is that it is difficult to create a mold for complex shapes that is capable of releasing the shape once the material within the mold has hardened. One common solution is to split the mold so as to enable the form to be released after it has hardened.
A much more difficult problem is to create structures with complex external shapes accompanied with complex internal shapes. In fact, to the inventors' knowledge, there is no unitary mold capable of creating a structure with complex external and internal shapes.
In particular, in the field of dentistry, to treat damaged teeth, it is known how to make fairly simple external shapes for crowns. See for example, Updyke, et al., U.S. Pat. No. 5,775,913. Nonetheless, even these simple external shapes require the use of split forms in order to release those simple shapes from the mold. Again, a much more difficult problem, heretofore unsolved as far as the Applicants know, is the creation of not only complex external shapes, but in particular, the creation of complex internal shapes. While the prior art has focused on the creation of reasonably accurate reproductions of the external shapes of teeth, there has been no solution for the creation of the internal portion of a structure, crown, to incorporate complex internal shapes mirroring the complex external shapes found in an actual tooth. In fact, to Applicants' knowledge, the internal structure of the crowns known in the art at best are designed to accommodate a rectangular shaped tooth (see e.g. Updyke, et al., U.S. Pat. No. 5,775,913), and at worst and more typically, a "TP" form. That is to say, the application of crowns in the prior art required the preparation of the diseased or damaged tooth into a shape readily accommodated by the crown and a shape which would allow the removal of the crown in the future. This shape, in the form of a tapering trapezoid from the base to the top of the tooth, is illustrated over and over again in the prior art. (See e.g. Dzilki, et al., U.S. Pat. No. 4,854,875 and Bryan, U.S. Pat. No. 4,850,871) The creation of this traditional TP in dentistry results in the destruction of portions of perfectly healthy teeth in order to accommodate prior art crowns.
Goracci, et al., disclose in the July, 1999 issue of Compendium, in an article entitled "Aesthetic and Functional Reproduction of Occlusal Morphology With Composite Resins", a process for repairing teeth with minor dental decay. This process essentially includes the creation of a mold of the exterior of the tooth prior to removal of the dental decay. The dental decay is removed, then filled and the exterior mold is placed over the tooth until the filling material hardens, at which time the exterior mold is removed. As the authors themselves point out, however, an important limitation of this method is that it can be used only when the occlusal surface of the tooth is not damaged by the carious lesion.
As a result, there is a need in the art for providing an apparatus and method for creating a structure with complex external and internal shapes. It, therefore, is an object of this invention to provide an improved apparatus and method for creating a structure with complex external and internal shapes which does not require single or multiple split molds, which is easy to use, and which is capable of repetitive use for the creation of multiple, essentially identical structures.